1 / 24

STELLAR EVOLUTION

STELLAR EVOLUTION. The life cycle of stars. EMPTY SPACE?. So called empty space actually has a density of .1 to 1 particles per cubic centimeter. Also present are quantum virtual particle pairs and all sorts of energetic disturbances such as supernova shock waves, gravity waves, and radiation.

cybill
Télécharger la présentation

STELLAR EVOLUTION

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. STELLAR EVOLUTION The life cycle of stars.

  2. EMPTY SPACE? • So called empty space actually has a density of .1 to 1 particles per cubic centimeter. • Also present are quantum virtual particle pairs and all sorts of energetic disturbances such as supernova shock waves, gravity waves, and radiation.

  3. GIANT MOLECULAR CLOUD • Gravity sometimes accretes material to increase the density of space. • Giant molecular clouds have densities ranging from 10 to one million particles per cubic centimeter.

  4. GRAVITATIONAL COLLAPSE • Mechanism of gravitational collapse is unknown but might be caused by shock waves. • The GMC collapses and fragments to form Bok Globules (star forming cocoons).

  5. PROTOSTAR FORMATION • The loss of gravitational potential energy causes heating. • Protostars fall into three categories depending on their mass. • Small protostars less than .1 solar mass (SM). • Medium protostars 1-50 SM. • Massive protostars >50 SM.

  6. PROTOSTAR

  7. FAILED STARS • Less than .1 SM does not have enough mass to produce fusion. • These Brown Dwarfs are very numerous and may account for some of the “dark matter” theorized by cosmologists.

  8. FUSION BEGINS • Protostars with masses of >.6 SM undergo gravitational collapse. • Heat and pressure increase until hydrogen fusion begins. • The “birth of the star” blows away dust and gas from the cocoon. • These new stars become Main sequence stars.

  9. A STAR NURSERY

  10. MAIN SEQUENCE STARS • Burn hydrogen in their cores. • They establish hydrostatic equilibrium. • Outward pressure from fusion and the Coulomb force = inward force due to gravity.

  11. SMALL MAIN SEQUENCE STAR • Mass is .5 SM or less. • Live for hundreds of billions of years. • Usually called COOL RED DWARF STARS.

  12. MID SIZED STARS • Mass is .6 – 5.4 SM. • Live for approximately 10 billion years. • Our sun is a mid sized main sequence star.

  13. GIANT STARS • Live for only a few million years. • They are between 10-20 SM. • They burn their hydrogen very rapidly to maintain hydrostatic equilibrium.

  14. GOING OFF MAIN SEQUENCE • After all of the hydrogen fuses, the star undergoes main sequence turnoff. • The hydrostatic pressure decreases and the star begins collapse. • Wolf Rayet type stars.

  15. GERIATRIC LOW MASS STARS • Stars less than .5 SM. • Too small to fuse helium. • Fade and evaporate to form Brown Dwarf Stars.

  16. MEDIUM STAR • Stars less than 3.4 SM. • Helium fuses to form carbon. • Luminosity and core temperature increase. • Surrounding gas bloats out to form a Red Giant.

  17. RED GIANT DEMISE • Large energy pulsations eject most of the solar material. • This material may recycle to form new stars. • The star shrinks to form a White Dwarf.

  18. BINARY SYSTEM WHITE DWARF • A white dwarf in a binary system can accrete material from its partner star to build up mass again. • Little hydrostatic pressure causes rapid collapse and a Type 1A supernova.

  19. GIANT OR SUPER GIANT STAR • Stars of > 3.5 SM. • Huge gravitational pressure collapses the core. • Temperatures increases and fusion continues until Iron is formed. • Iron can not undergo fusion and the hydrostatic pressure drops.

  20. CORE COLLAPSE • Rapid end of fusion causes very fast core collapse. • The collapse happens in a fraction of a second. • This causes a Type 2 supernova.

  21. NEUTRINO SHOCK WAVES • The supernova causes shock waves of neutrinos. • Most of the stellar material is blasted out into space. • The escaping material is bombarded with neutrinos. • The neutrinos are captured and elements heavier than iron are formed.

  22. SMALL STARS • Stars < 1.5 SM. • Gravity collapses them until electron degeneracy stops collapse. • White dwarf forms. • Evaporates to form a Black Dwarf.

  23. MID SIZED STARS • Mass is > 1.4 and < 3 SM. • The collapse forces the electrons into the nucleus where they combine with protons to form neutrons. • Neutron or quark stars are formed.

  24. MASSIVE STARS • Mass > 3 SM. • Gravity overcomes neutron degeneracy and collapses the core to form a Singularity. • A black hole results.

More Related